JPH0730933Y2 - Fuel supply device for LPG engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel supply device for an engine that uses LPG, that is, liquefied petroleum gas as a fuel, especially for a high-power engine.

(Prior Art) In a fuel supply device for an LPG engine, generally, a mixer (mixer) is arranged in an intake passage of the engine, and an LPG cylinder is supplied between the LPG cylinder for fuel storage and the mixer. A pressure adjusting device called a vaporizer, which vaporizes and adjusts the pressure of the fuel and sends it to the mixer, is provided. The vaporizer is a two-stage depressurization type having a primary chamber for depressurizing the LPG fuel and maintaining it at a predetermined pressure, and a secondary chamber for further depressurizing the fuel from the primary chamber and delivering it. Commonly used.

By the way, the LPG engine used to be mounted on a relatively small vehicle such as a taxi.
Even in heavy-duty trucks, LPG is now becoming a reality from the viewpoints of exhaust gas regulations and noise. However, regarding the LPG of high-power engines such as large trucks, in the conventional technology, by increasing the size of the vaporizer and increasing the size of the mixer, fuel consumption is particularly high at high loads and high revolutions. It is necessary to secure the supply amount, which causes restrictions on layout, and causes problems such as unstable fuel supply in a small flow rate use area such as idling and requiring separate measures. Moreover, even if the vaporizer and the mixer are increased in size in this way, the fuel followability is insufficient in the region of medium speed rotation or higher, and it is still difficult to achieve the required output. Further, if the internal pressure of the primary chamber of the vaporizer is increased in order to improve the fuel followability, this time, it becomes difficult to control the fuel in the low load / rotation range including the idle. Further, conventionally, as described in, for example, Japanese Patent Laid-Open No. 60-159358, the internal pressure of the primary chamber of the vaporizer is changed according to the engine load to improve the stability of the fuel supply amount in a small flow rate range. It has also been proposed to improve the fuel following performance in a high load operation range, but by adjusting the primary indoor pressure alone as described above, a high load / high load can be achieved especially in a high output engine such as a large truck. Insufficient fuel during rotation cannot be fully resolved.

(Purpose of the Invention) The present invention has been made in view of the above problems, and particularly in a fuel supply device for an LPG engine that requires a high output, at the time of high load and high rotation without increasing the size of the vaporizer. The purpose is to be able to solve the fuel shortage of.

(Structure of the Invention) The present invention focuses on the fact that the fuel shortage can be resolved by supplying the high pressure fuel to the secondary chamber of the vaporizer by bypassing the primary chamber when the engine is under high load and high rotation speed. The secondary lever that drives the secondary valve of the vaporizer is effectively used, and the configuration thereof is as follows. That is, the fuel supply device for an LPG engine according to the present invention comprises a primary chamber for depressurizing the LPG fuel and maintaining it at a predetermined pressure,
In a vaporizer having a secondary chamber for further reducing the pressure of the fuel from the primary chamber and delivering the fuel, a high pressure chamber for holding the LPG fuel supplied from a fuel storage cylinder in a high pressure state before entering the primary chamber. And a secondary valve for communicating the secondary chamber to the primary chamber is opened by the other end extension part of the secondary lever which holds the secondary chamber at the time of high load and high rotation of the engine. A high-pressure control valve that communicates with the high-pressure chamber is provided.

(Operation) The LPG fuel supplied from the fuel storage cylinder to the vaporizer enters the high-pressure chamber first, enters the primary chamber from the high-pressure chamber, is vaporized, and is held in a state of being depressurized to a predetermined pressure. Then, the fuel held in the primary chamber is metered through the secondary valve, enters the secondary chamber, is further depressurized, and is delivered.

Further, when the engine is under high load and high rotation, the high pressure control valve is opened by the secondary lever. As a result, the high-pressure fuel held in the high-pressure chamber is directly supplied to the secondary chamber, and the required amount of fuel is delivered.

(Example) Hereinafter, an example will be described with reference to the drawings.

The figure shows a vaporizer 1 according to an embodiment of the present invention. This vaporizer 1 is provided with a casing 2 having a partition wall 2a at its central portion and having both ends open, and cover members 3 and 4 for covering both ends of the casing 2. The partition wall 2a is provided between the casing 2 and the one cover member 3.
A primary valve diaphragm 6 that forms a primary chamber 5 is installed between the casing 2 and the cover member 4 on the opposite side of the partition wall 2a from the primary chamber 5. A secondary valve diaphragm 8 forming a secondary chamber 7 is mounted.

The partition wall 2a is provided with a communication passage 9 at a side portion thereof, which communicates with the primary chamber 5 and the secondary chamber 7.
The valve seat member 10 is attached from the side. Further, the central portion of the partition wall 2a bulges toward the primary chamber side, and the secondary chamber 7 side thereof is partitioned by the vacuum lock-off diaphragm 11 to form a vacuum lock-off chamber 12. The vacuum lock-off chamber 12 is connected to an intake passage (not shown) downstream of the throttle valve of the engine. The partition wall 2a located on the side opposite to the communication passage 9 with respect to the central portion
A high pressure chamber 15 defined by a diaphragm (high pressure valve diaphragm) 13 and a partition plate 14 is formed on the side of the secondary chamber 7 side, and the high pressure chamber 15 communicates with the primary chamber 5. A passage 16 is provided, and a valve seat member 17 is attached to the communication passage 16 from the primary chamber 5 side.

The high pressure chamber 15 penetrates the casing 2 and is not shown.
A fuel introduction path 18 connected to the LPG cylinder is provided. The tip of the fuel introduction passage 18 opens at a position facing the center of the high pressure valve diaphragm 13, and a valve seat 19 is provided at the opening.
Is provided. On the other hand, a high pressure valve 20 which is seated on the valve seat 19 from the inside of the fuel introduction passage 18 is fixed to the high pressure valve diaphragm 13. A coil spring (high pressure valve diaphragm spring) 21 is installed between the high pressure valve diaphragm 13 and the partition wall 2a of the casing 2 so that the high pressure valve 20 is constantly urged in the opening direction by the spring 21. ing. Also, this spring is attached to the partition wall 2a.
A screw (high pressure adjusting screw) 22 for adjusting the biasing force of 21 is provided.

A communication passage 23 that connects the high pressure chamber 15 and the secondary chamber 7 is formed in the partition plate 14 that divides the high pressure chamber 15. The communication passage 23 is a tapered hole that widens on the high pressure chamber 15 side, and a tapered valve (high pressure control valve) 24 is arranged so as to be seated from the high pressure chamber 15 side. High pressure control valve 24 rod part 24
a extends to the secondary chamber 7 side and penetrates the valve box 25 fixed to the partition plate 14. Further, a spring receiving member 27 that holds a coil spring 26 between the partition plate 14 and the valve box 25 is fixed to the rod portion 24a. The valve box 25 is provided with a through hole 28 that communicates the inside with the secondary chamber 7. A primary valve 29 is arranged at a position facing the valve seat member 17 of the communication passage 16 that connects the high pressure chamber 15 and the primary chamber 5. This one
The secondary valve 29 is held at one end of a primary lever 32 whose midway portion is supported by a support shaft 31 of a casing 2 side support member 30. The other end of the primary lever 32 has two U-shaped leaf springs 33, 3 fixed to the central position of the primary valve diaphragm 6.
It is sandwiched between 4. On the side opposite to the primary chamber 5 of the primary valve diaphragm 6, a primary lever 32 is opened between a screw (primary pressure adjusting screw) 35 screwed into the cover member 3 on the primary side. A coil spring (primary valve diaphragm spring) 36 that urges in the direction is attached.

On the other hand, a secondary valve 37 is arranged at a position facing the valve seat member 10 of the communication passage 9 that communicates the primary chamber 5 and the secondary chamber 7. The secondary valve 37 is held at one end of a secondary lever 40 whose middle portion is supported by a support shaft 39 of a support member 38 on the casing 2 side. Then, the secondary valve 37 is sandwiched by the support shaft 39.
A coil spring (secondary valve diaphragm spring) 42 for urging the secondary lever 40 in the valve closing direction is provided between the spring receiving member 41 and the spring receiving member 41 screwed to the supporting member 38. ing.

The other end of the secondary lever 40 is connected to the secondary valve diaphragm 40.
Of the high pressure control valve 24 is extended beyond the position facing the central portion of the high pressure control valve 24, and the extension 40a faces the head of the rod portion 24a of the high pressure control valve 24. Secondary valve 37
Is closed, the rod portion 24a and the extending portion 40a of the secondary lever 40 face each other with a predetermined gap. And
When the secondary lever 40 rotates a predetermined amount in the valve opening direction, the extension portion 40
a presses the rod portion 24a to open the high pressure control valve 24.

A support pin 43 that abuts and supports the secondary lever 40 is projectingly provided at the center of the secondary valve diaphragm 8. Further, the secondary lever 40 is engaged with a stopper 44 fixed to the vacuum lock-off diaphragm 11, and its rotation in the valve opening direction is normally restricted.

Further, a pressure adjusting lever 46 holding a coil spring 45 for urging the secondary valve diaphragm 8 toward the secondary chamber 7 side is provided at one end inside the cover member 4 on the secondary side.
The lever 46 has a midway portion supported by a support shaft 47, and a coil spring 48 for biasing the lever 46 in the return direction on the other end side.
Is provided. Further, a cam 49 that engages with the other end of the lever 46 is provided, and an adjusting screw 50 that rotates the cam 49 is provided. When the cam is rotated around the support shaft 51 by the adjusting screw 50, the biasing force of the coil spring 45 with respect to the secondary valve diaphragm 8 changes, and the valve opening pressure of the secondary valve is adjusted.

A fuel delivery path 52 connected to a mixer (not shown) is opened in the secondary chamber 7.

The LPG fuel supplied from an LPG cylinder (not shown) is a high pressure valve.
The liquid enters into the high pressure chamber 15 via 20. When the internal pressure of the high-pressure chamber 15 acting on the high-pressure valve diaphragm 13 is lower than the set pressure, the high-pressure valve 20 opens, and when it is higher than the set pressure, the high-pressure valve 20 closes, so that the internal pressure of the high-pressure chamber 15 is maintained at a predetermined pressure. It In addition, the primary chamber 5 has a primary valve diaphragm spring 36.
The internal pressure is defined by, and if the internal pressure is lower than the predetermined pressure, 1
The next valve 29 opens and fuel flows from the high pressure chamber 15.

When you start engine cranking. Since the vacuum lock-off chamber 12 has a negative pressure and the vacuum lock-off diaphragm 11 is pulled, the secondary lever 40 is in a free state. Then, after that, fuel corresponding to the negative pressure generated in the venturi portion of the mixer is delivered from the fuel delivery passage and the secondary valve diaphragm 8 is pulled, and the pressing force of the support pin and the secondary valve diaphragm spring by the secondary valve diaphragm 8 are pulled. Secondary lever 40 in balance with the spring force of 42
Rotates to open and close the secondary valve 37, whereby the metered fuel flows in from the primary chamber 5.

Also, when the Venturi negative pressure becomes a high load or high rotation above a certain pressure, the secondary lever 40 pivots largely in the valve opening direction, and its extending portion 40a presses the rod portion 24a of the high pressure control valve 24. Causes the high pressure control valve 24 to open. Thereby, high-pressure fuel is directly supplied to the secondary chamber 7, and a large amount of fuel is delivered to the mixer.

(Effects of the Invention) Since the present invention is configured as described above, a high load and a high load can be achieved with a simple configuration without increasing the size of the vaporizer.
It is possible to prevent the fuel shortage at the time of high rotation.

[Brief description of drawings]

FIG. 1 is a sectional view of a vaporizer according to an embodiment of the present invention. 1: Vaporizer, 5: 1 Primary chamber, 7: Secondary chamber, 13: High pressure valve diaphragm, 15: High pressure chamber, 9, 16, 23: Communication passage, 18: Fuel introduction passage,
20: high pressure valve, 21: high pressure valve diaphragm spring, 24: high pressure control valve, 29: primary valve, 37: secondary valve, 40: secondary lever, 52: fuel delivery passage.

Claims (1)

[Scope of utility model registration request] 1. A vaporizer having a primary chamber for reducing the pressure of LPG fuel to maintain it at a predetermined pressure, and a secondary chamber for further reducing the pressure of the fuel from the primary chamber and delivering the fuel, which is supplied from a fuel storage cylinder. A high pressure chamber for holding the LPG fuel in a high pressure state before entering the primary chamber is provided, and a secondary valve for communicating the secondary chamber with the primary chamber is held at one end of a secondary lever. A fuel supply device for an LPG engine, comprising a high pressure control valve which is opened by the other end extending portion and which communicates the secondary chamber with the high pressure chamber when the engine is under high load and high rotation.